% Copyright 2020 Makani Technologies LLC
%
% Licensed under the Apache License, Version 2.0 (the "License");
% you may not use this file except in compliance with the License.
% You may obtain a copy of the License at
%
%      http://www.apache.org/licenses/LICENSE-2.0
%
% Unless required by applicable law or agreed to in writing, software
% distributed under the License is distributed on an "AS IS" BASIS,
% WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
% See the License for the specific language governing permissions and
% limitations under the License.

function [q] = mrp_to_q(p)
% mrp_to_q -- Convert a modified Rodrigues parameter to a quaternion.

pp = dot(p, p);
q.s = (1 - pp) ./ (1 + pp);
q.v = 2 * p;
q.v(1, :) = q.v(1, :) ./ (1 + pp);
q.v(2, :) = q.v(2, :) ./ (1 + pp);
q.v(3, :) = q.v(3, :) ./ (1 + pp);
end
